The dynamic desorption of krypton from the zeolite chabazite.

Single crystal diffraction studies of the zeolite chabazite show that at high loading krypton atoms are forced to occupy sites with unfavourable interatomic Kr-Kr separations but upon desorption of Kr the remaining Kr atoms can now occupy sites with no such unfavourable separations.

Characterisation of airborne particulate pollution in the Cu smelter and former mining town of Karabash, South Ural Mountains of Russia.

Airborne total suspended particulates (TSP), dusts from smelter blast furnace and converter stacks, and filtrates of snow melt waters have been characterised in the Cu smelter and former mining town of Karabash, Russia. TSP was collected at sites up- and downwind of the smelter and large waste and tailings dumps (Oct. 2000 and July 2001). Methods for particle size, mineralogical and elemental determinations have been tested and described, and a new PSD-MicroSOURCE XRD technique developed for the mineralogical analysis of microsamples on filter substrates. TSP in downwind samples has a mean equivalent spherical diameter of 0.5 microm (s.d. = 0.2) and was found to be 100% respirable. The main element of human health/environmental concern, above Russian maximum permitted levels (1 microg m(-3), average over any time period), was Pb which was measured at 16-30 microg m(-3) in downwind samples. Individual particulates mainly consisted of complex mixtures of anglesite (PbSO4), Zn2SnO4 and poorly ordered Zn sulphates. From experimental and theoretical considerations, a high proportion of contained Pb, Zn, Cd and As in this material is considered to be in a readily bioavailable form. Chemical and mineralogical differences between the TSP, stack dusts and snow samples are discussed, as well as the implications for human and regional environmental health.

Observations of the impacts of some landfill leachates with clays.

Compacted clay liners are common, major, components of landfill leachate (fluid) containment systems. This is sensible, but knowledge and understanding of the longterm performance and behaviour of day mineral/landfill leachate systems remain very limited. The authors studied the reactions of day soil with leachate simulants related to three different climates and waste cultures. The day came from a Tertiary sequence near Melbourne, Australia, a type in common use locally for landfill engineering. X-ray diffraction was used to observe mineralogical change in 3 mm clay plugs caused by reactions with the leachate simulants. Changes in hydraulic conductivity were also measured. The results show both that the different leachates have distinct effects on the clay minerals, and that the leachate/day reactions have direct measurable and distinct impacts on hydraulic conductivity. The laboratory studies were completed at the University of Melbourne. The X-ray diffraction work was completed at The Natural History Museum in London. The experimental results are discussed here and indications given of some potential implications.

Development of X-ray photoemission electron microscopy (X-PEEM) at the SRS.

The use of synchrotron radiation sources for X-ray spectroscopy is a well known and developed field. The majority of applications, however, have been limited to studies of materials containing only a single phase of the element of interest. Owing to limited availability of suitable instrumentation, the study of materials comprising intergrowths of different phases has presented difficulties in analysis. The majority of natural materials, including mineralogical samples, fall into this category. However, by applying the technique of photoemission electron microscopy (PEEM) to view the X-ray stimulated photoemission generated at an absorption edge, micro-area-selectable spectroscopy becomes possible. An instrument for X-ray PEEM (X-PEEM) is being developed at the Daresbury SRS and this paper shows how it can be used to obtain characteristic L-edge XANES spectra from finely intergrown iron oxide minerals.

2p X-ray Absorption Spectroscopy in the Earth Sciences.

A complete knowledge of 3d transition-metal valencies, site occupancies and site symmetries is essential for a full understanding of mineral/melt energetics and behaviour. Over the last few years, significant advances in both instrumentation and theory associated with synchrotron radiation sources and experiments have enabled the development of 2p X-ray absorption spectroscopy as a sensitive, element-specific site and valency probe. The potential of this technique in the Earth sciences is discussed in this paper with examples reflecting the variety of problems set by 3d transition metals in natural systems.